Well, just to be the devil's advocate here, the chances of him surviving those operations and procedures that modern science and medicine were very slim.
I'm sure somewhere in his speeches he probably said he could've died a number of times during those operations. So I'm sure he thanks God for the being the 1%, as it were.

But I'm sure he doesn't only believe god saved him.
I think he probably knew the risk of the operations only after they happened and was told what a small chance he had, yet survived nonetheless.
Miracles happen. People come through despite the odds being overwhelmingly against them.
And for that, they thank God, because it was a tiny chance, yet they came out just fine.
Faith isn't really the answer to everything. Sure it's rather stupid to solely rely on your faith to have God save you.
But it can calm people down, relax them, and help them cope with traumatic circumstances.
Surely you can't deny someone their right to choose what ever that calms them down.

Actually, doctors always tell their patients (unless asked otherwise) the risks of the operation. They have to sign paperwork to get the operation, letting them know of the risks they are taking. Faith has been shown to have no affect on people while under the knife. Atheists and Christians do the same during surgery.

I can't and won't deny someone the right to faith, but I'll damn sure call them out when they don't give credit where it's truly due.

In a life or death situation, usually the doctors don't stop for a while and explain the risks to the patients, because time is crucial. So maybe he didn't know the risks until later, and didn't know how close he came to dying.
And again, I'm sure somewhere in his speeches he thanks the doctors as well as God.

He mainly does talks about faith, though. I'm sure he's given a thank you or two, but his real message is about god. In an emergency situation, it's up for family members to decide whether or not to get the surgeries if the patient isn't conscious. If the patient is, then they'll still be asked and given info, not specific of course, about how dangerous it is.